轉載：http://www.cnblogs.com/hibraincol/archive/2011/10/27/2227149.html
今天在看android froyo的launcher2 源碼的時候，在launcher.xml中看到有這麼一段代碼：
<com.android.launcher2.DragLayer xmlns:android="http://schemas.android.com/apk/res/android" xmlns:launcher="http://schemas.android.com/apk/res/com.android.launcher" android:id="@+id/drag_layer" android:layout_width="match_parent" android:layout_height="match_parent"> <include layout="@layout/all_apps" /> <!--
The workspace contains 3 screens of cells --> <com.android.launcher2.Workspace android:id="@+id/workspace" android:layout_width="match_parent" android:layout_height="match_parent" android:scrollbars="horizontal" android:fadeScrollbars="true" launcher:defaultScreen="2"> |
注意到其中的兩處：
xmlns:launcher=”http://schemas.android.com/apk/res/com.android.launcher”
和
launcher:defaultScreen="2"
可以看出在這個佈局文件中，使用了自定義屬性。
以前沒遇到過，既然這裏碰到了，就順便學習下，下面就寫個簡單的示例，權當學習筆記，便於以後查閱。
1. 定義一些自定義屬性
建立一個屬性xml文件： values/attrs.xml, 內容如下：
<?xml version="1.0" encoding="utf-8" ?><resources> <!--
the relation between the icon and text. --> <attr name="relation"> <enum name="icon_left" value="0" /> <enum name="icon_right" value="1" /> <enum name="icon_above" value="2" /> <enum name="icon_below" value="3" /> </attr> <skip /> <declare-styleable name="IconText"> <attr name="relation" /> <attr name="icon" format="reference" />
<attr name="text" format="string" /> <attr name="text_size" format="dimension" /> <attr name="text_color" format="integer" /> <attr name="space" format="dimension" /> </declare-styleable> </resources> |
解釋如下：
屬性relation有4種可選值：icon_left, icon_right, icon_above,icon_below.
屬性icon的可選值爲引用： 例如："@/drawbable/icon".
屬性text的可選值爲string， 例如： "Hello world", 也可是string的引用"@string/hello".
屬性text_size的可選值爲尺寸大小，例如：20sp、18dip、20px等.
屬性text_color的可選值爲整數，例如："0xfffffff"， 也可以是color的引用"@color/white".
2. 定義一個能夠處理這些屬性值的view或者layout類
package com.braincol.viewattrs;import android.content.Context;import android.content.res.TypedArray;import android.util.AttributeSet;import android.util.Log;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.TextView;public class IconTextView
extends LinearLayout
{ private final static String
TAG = "IconTextView"; private final int ICON_LEFT
= 0; private final int ICON_RIGHT
= 1; private final int ICON_ABOVE
= 2; private final int ICON_BELOW
= 3; private TextView
mTextView; private ImageView
mImageView; private int mRelation
= ICON_LEFT; private String
mText = ""; private int mIconId; private float mTextSize; private int mSpace; public IconTextView(Context
context, AttributeSet attrs){ super(context,
attrs); TypedArray
a = context.obtainStyledAttributes(attrs, R.styleable.IconText); mRelation
= a.getInt(R.styleable.IconText_relation, ICON_LEFT); Log.d(TAG,"mRelation:
"+mRelation); mText
= a.getString(R.styleable.IconText_text); Log.d(TAG,"mText:
"+mText); mTextSize
= a.getDimensionPixelSize(R.styleable.IconText_text_size, 12); Log.d(TAG,"mTextSize:
"+mTextSize); mSpace
= a.getDimensionPixelSize(R.styleable.IconText_space, 5); Log.d(TAG,"mSpace:
"+mSpace); mIconId
= a.getResourceId(R.styleable.IconText_icon, R.drawable.icon); Log.d(TAG,"mIconId:
"+mIconId); a.recycle(); mTextView
= new TextView(context); mTextView.setText(mText); mTextView.setTextSize(mTextSize); mImageView
= new ImageView(context); mImageView.setImageResource(mIconId);
int left
= 0; int top
= 0; int right
= 0; int bottom
= 0; int orientation
= HORIZONTAL; int textViewIndex
= 0; switch(mRelation){ case ICON_ABOVE: orientation
= VERTICAL; bottom
= mSpace; textViewIndex
= 1; break; case ICON_BELOW: orientation
= VERTICAL; top
= mSpace; break; case ICON_LEFT: right
= mSpace; textViewIndex
= 1; break; case ICON_RIGHT: left
= mSpace; break; } this.setOrientation(orientation); this.addView(mImageView); mImageView.setPadding(left,
top, right, bottom); this.addView(mTextView,
textViewIndex); }} |
可以看出這個LinearLayout 子類IconTextView中只有兩個元素，ImageView 和mTextView，通過從xml配置文件中讀取屬性值來決定icon和text的內容、相對位置及其它屬性。
3. 在layout佈局文件中使用這個自定佈局及其屬性
layout/main.xml:
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" ><com.braincol.viewattrs.IconTextView android:id="@+id/icontext_01" xmlns:android="http://schemas.android.com/apk/res/android" xmlns:icontext="http://schemas.android.com/apk/res/com.braincol.viewattrs" android:layout_width="wrap_content" android:layout_height="wrap_content" icontext:relation="icon_left" icontext:icon="@drawable/hi" icontext:text="hi,how
are you!" icontext:text_size="12sp" /> </LinearLayout> |
可以看到我們在這個佈局文件中加入了一個新的命名空間：
xmlns:icontext="http://schemas.android.com/apk/res/com.braincol.viewattrs"
並使用我們自定義的那些屬性：
icontext:relation="icon_left"
icontext:icon="@drawable/hi"
icontext:text="hi, how are you !"
icontext:text_size="30sp"
4. 在Activity中使用該佈局
package com.braincol.viewattrs;import android.app.Activity;import android.os.Bundle;public class ViewAttrs
extends Activity
{ /**
Called when the activity is first created. */ @Override public void onCreate(Bundle
savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); }} |